DuplicateDependency.qhelp

<!DOCTYPE qhelp PUBLIC
  "-//Semmle//qhelp//EN"
  "qhelp.dtd">
<qhelp>

<overview>
<p>
  Dependency injection in AngularJS is done by providing the names of
  the desired dependencies. Providing the same name multiple times is
  redundant since the AngularJS injector uses a cache for instantiated
  dependencies.
</p>
</overview>

<recommendation>
<p>
Only include the name of each dependency once.
</p>
</recommendation>

<example>
<p>
The following example shows an AngularJS controller with <code>$cookies</code> as a duplicate dependency.
</p>

<sample src="examples/DuplicateDependency.js"/>

<p>
This is problematic, since the programmer could be led to believe that the two parameters <code>$cookies1</code> and <code>$cookies2</code> are different instances, which they are not.
</p>

<p>
Instead, the dependency should only be listed once:
</p>

<sample src="examples/DuplicateDependency-fixed.js"/>
</example>

<references>
<li>AngularJS Developer Guide: <a href="https://docs.angularjs.org/guide/di">Dependency Injection</a>.</li>
</references>
</qhelp>